A presence service is also referred to an existence service, which is a communication service for collecting and distributing presence information. At present, the presence service is usually provided together with an instant message service. Alternatively, the presence service may also be provided independently, or in conjunction with other services, such as network game services. Standard specifications related to presence services have been worked out preliminarily by international standard organizations, such as Internet Engineering Task Force (IETF) and Open Mobile Alliance (OMA), and are now being perfected continually. The present invention mainly uses terms in RFC 2778, and calls an entity or user providing presence information to the presence service as a presentity and an entity or user requesting presence information from the presence service as a watcher. A user of the presence service may be a natural person or a non-natural person, i.e. the presentity and watcher both may correspond to natural persons or non-natural persons. In addition to basic information such as online/offline status and communication mode of the presentity, the presence information also includes extended information such as mood, location, and activity; and value-added service information provided by the non-natural person such as weather forecasting, station, or TV program, and traffic movement. Relevant standard drafts released by IETF and OMA are at present for the natural person and no study is carried out for publishing of presence information of the non-natural person, and presence information of the non-natural person is not provided in instant message service already placed into the commercial application. In fact, the publishing of presence information of the non-natural person differs greatly from that of the natural person.
An architecture diagram of an existing presence service system is shown in FIG. 1, in which natural person presentities 11, 12, and 13 directly publish respective presence information to a presence server 14 and the presence server distributes these presence information to corresponding watcher clients 15. If the non-natural person presentity is directly connected with a certain presence server and the presence server directly distributes presence information to watcher clients over a SIP/IP (Session initiation protocol/Internet Protocol) core network, when the amount of information service traffic of the non-natural person presentity is large, all presence information is forwarded by the presence server directly connected therewith, which would exert an extreme large load on the presence server and is difficult to meet the requirements of service development. Moreover, since, in general, it is the presence server of a user's home that is responsible for forwarding of user presence service information, if this presence server is not connected with the non-natural person presentity providing service, when the user acquires presence information with a one-time subscription, the subscription request message will not be sent to the non-natural person presentity. Further, for different non-natural person presentities, such as radio station presentity and transportation information presentity, formats of provided presence information contents are different and it is difficult to abstract a data model similar to that of the natural person to describe presence information of the non-natural person generally. In addition, information provided by the non-natural person presentity to a watcher client is usually charged and rates are usually different for information provided by different non-natural persons. The above differences make it difficult to similarly process presence information of the non-natural person in the same manner as that of the natural person. Therefore, with development of the presence service for the forwarding of information type presence information, the user's presence information should be transmitted by the presence server of the user's home. However, the main problems required to be resolved for development of the presence service are how to access numerous kinds of non-natural person presentities to presence servers everywhere and how to ensure conformity and security of the access to separate access and control of the presence service.